(* generate a random planar polygon, with specified number of sides *)
A1 = RandomVariate[NormalDistribution[0,1],500];
A2 = RandomVariate[NormalDistribution[0,1],500];
{B1, B2} = Orthogonalize[{A1, A2}];
C1 = B1^2 - B2^2;
C2 = 2 * B1 * B2;
Pts = Transpose[{C1, C2}];
SumPts = Join[{{0,0}},Accumulate[Pts]];
ListLinePlot[SumPts]